Passenger Radial Tire Carcass Layout for Contact Patch Shape
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Solution Overview
Problem
Pneumatic radial tires with narrow width and large diameter, when using only one inclined belt layer, suffer from deteriorated ground contact patch shape due to high belt cord stiffness, leading to decreased driving performance, especially at high internal pressures.
Innovation Solution
A pneumatic radial tire design with a cross-sectional width less than 165 mm and a ratio of cross-sectional width to outer diameter of 0.26 or less, featuring a single inclined belt layer, a carcass with radial and angled carcass cord arrangements, and intersecting carcass and belt cords to promote tread rubber stretching, enhancing ground contact patch shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If only one inclined belt layer is used, then tire weight is reduced and fuel efficiency is improved, but the ground contact patch shape deteriorates due to high belt cord stiffness
Solution Approach 1:
The carcass cords are arranged radially only in the second tire widthwise portion (outer side when mounted on vehicle) where ground contact occurs, while allowing inclined belt cords to provide stiffness in the crown portion. This localized radial arrangement allows the tread rubber to stretch properly in the ground contact area, improving ground contact patch shape while maintaining the single inclined belt layer configuration for weight reduction.
Solution Approach 2:
The carcass is divided into different widthwise portions with different cord arrangements: a first tire widthwise portion and a second tire widthwise portion. The second portion (located on the outer side when mounted on vehicle) has carcass cords arranged radially to specifically address ground contact patch shape, while other portions can have different arrangements. This segmentation allows targeted optimization of different tire regions.
2Use of energy by moving object
If the cross-sectional width is made small and outer diameter is made large, then fuel efficiency is improved through reduced air resistance, but the ground contact patch shape deteriorates due to high internal pressure effects
Solution Approach 1:
The radial arrangement of carcass cords is specifically applied to the second tire widthwise portion on the outer side, which is the region most affected by high internal pressure in narrow-wide tires. This localized structural optimization addresses the ground contact patch shape issue caused by high internal pressure while maintaining the narrow width and large diameter configuration for improved fuel efficiency.
3Strength
If belt cords are arranged at an angle to the tire circumferential direction, then tire strength is improved, but the tread rubber cannot stretch in the extending direction of the belt cords
Solution Approach 1:
The inclined belt layer is positioned primarily in the crown portion of the tire where strength is most needed, while the carcass cords are arranged radially in the second tire widthwise portion (ground contact area) to allow tread rubber to stretch. This spatial separation of functions allows the inclined belt to provide strength where required while the radial carcass arrangement enables proper tread deformation in the contact patch area.
Solution Approach 2:
The solution addresses the stretching limitation in the circumferential direction by utilizing the radial dimension through radially arranged carcass cords in the second tire widthwise portion. This dimensional approach allows the tread rubber to stretch radially in the ground contact area while the inclined belt maintains circumferential strength in the crown portion.
Data Source
AI summary
Provided is a pneumatic radial tire for passenger vehicles in which the cross-sectional width SW of the tire and the outer diameter OD of the tire satisfy a predetermined relationship, the carcass has a first tire widthwise portion in which the carcass cords are in a radial arrangement and a second tire widthwise portion in which the carcass cords extend at an angle to the tire circumferential direction, the second tire widthwise portion is located in a tire width-direction half which is on the outer side when the tire is mounted on a vehicle, and the carcass cords of the carcass body portion in the second tire widthwise portion and the belt cords extend in a direction that intersects each other when viewed from the outer side in the tire radial direction.